Many types of motorcycles exist which utilize a variety of engine types and operating temperature regulating apparatus and methods. Some motorcycles employ water cooling systems through the use of radiators and water passages within the engine block and other engine or transmission components. By far the most common type of motorcycle engine today, however, is an air-cooled engine comprising a lightweight aluminum engine block and cooling fins integrated around cylinders to dissipate accumulated heat from the engine generated from combustion and component friction within the engine.
Notably, motorcycles manufactured by Harley-Davidson Motorcycle Company of Milwaukee, Wis. have large displacement, air-cooled four stroke engines which, as is true for the vast majority of motorcycle engines, comprise an engine lubrication system comprising a least one oil pump which circulates oil through the engine for lubricating the components thereof, and for carrying away the accumulated heat of combustion and friction generated within the engine during operation.
Such large displacement, air-cooled four-stroke engines of current art, such as those manufactured by Harley-Davidson Motorcycle Company, typically utilize two different types of oil pumps for circulating oil through the lubrication system, namely a scavenge pump and a lubricating pump. The scavenge pump draws oil from the crank case area, then returns the oil to the oil reservoir, and the lubrication pump is utilized for circulating oil through the remainder of the system. To maintain adequate oil flow the scavenge pump is typically designed to operate at approximately 120 percent of the pump capacity of the lubricating pump, which is the supply pump of the system.
It is well-known in the art that, for such large displacement, air-cooled engines as described above, it is important that the operating temperature of the engine and lubricating oil reach a certain temperature after start-up from a cold start before operating the motorcycle on the road. Lubricating engine oil at ambient temperature has higher viscosity than at engine operating temperature, and because of this heavier consistency of cold oil, it does not flow easily through small oil passages within the engine block or oil cooling system. Further, upon cold start up, lubricating oil from the crank case takes a finite time to reach the components within the engine, and until such time after startup, cold metal-to-metal contact may occur between components within the engine, known as “hammer effect” in the art.
During operation of such a large displacement, air-cooled motorcycle as described above, the temperature range of the engine and therefore the lubricating oil may vary greatly depending on the circumstances of operation. For example, if the running motorcycle is stopped at a stop light or in traffic, or for any other reason during engine operation, cooling air is not adequately flowing around the finned cylinders and other portions of the engine, the temperature of the engine and lubricating oil may rise quickly to the point of oil thermal breakdown temperature, which quickly accelerates engine component friction and wear, significantly shortening the life of the engine.
It has been empirically determined by testing in the industry that the recommended minimum temperature for the lubricating oil for safely operating and maintaining engine life in such large displacement air-cooled four stroke engines as described above, should be at least 100 degrees Fahrenheit before operating the motorcycle. Empirical testing has also determined that the oil temperature should reach at least 100 degrees Fahrenheit before significantly raising the engine rpm and adding significant stress to the engine components, and after complete warm up and during operation of the motorcycle, a typical recommended temperature range for the oil is between approximately 170 degrees and 210 degrees Fahrenheit.
It is therefore desirable to maintain the oil operating temperature within the recommended range during all of the operating time of the motorcycle. It is also therefore desirable to be able to quickly raise the oil temperature upon start-up from a cold start, so as to shorten the potential time of “hammer effect” of cold metal-to-metal engine component contact.
Many motorcycles such as those described above manufactured by Harley-Davidson Motorcycle Company, for example, utilize oil cooling systems for attempting to maintain oil temperature. In such systems the lubricating oil is pumped from the crank case by a scavenge pump, first circulating through an oil filter, and is then diverted to a simple radiator-type oil cooler for cooling, and the cooled oil then circulates back to the reservoir.
In such systems, the oil cooler is typically mounted horizontally to the down tubes at the front of the frame of the motorcycle, transverse to the direction of travel of the motorcycle. Such an arrangement, however, has significant drawbacks in that oil cooling unit, for example, by being mounted unprotected on the front of the frame of the motorcycle, is exposed to damage from rocks, tar, and other road debris that may be kicked by the front tire of the motorcycle during operation, or by other vehicles sharing the road with the motorcycle. Further, depending on speed of travel of the motorcycle, conventional oil coolers mounted in such a way are not subjected to as much of the air circulation as may be required, due to the air flowing over a motorcycle traveling forward tending to divert under, over and around the front of the engine.
Another drawback in current art oil coolers and diverter apparatus is that, as equal amounts of oil are diverted to the oil cooler and by-passed back to the reservoir, the relatively excessive amount of oil pumped through the oil cooler at cold startup extends the period of time required for reaching the recommended operating temperature of the oil. The inventor has discovered that it is desirable, particularly at cold startup, to by-pass as much of the oil as possible back to the oil reservoir, provided that there remains at least a small portion of the total flow out of the oil filter diverted sufficient for dissipating condensation from within the crank case at cold start up, as typically happens with air-cooled aluminum block engines such as described.
It is therefore desirable to provide an oil cooling unit, system and method which overcomes all of several drawbacks described above for such current art oil cooling systems. An improved oil cooling unit, system and method is herein provided by the inventor, and is described below in enabling detail.